The present invention relates to videoconferencing systems, and more particularly, to optical orienting subsystems for videoconferencing systems. Such optics orienting arrangements are employed to facilitate a virtual face-to-face communication between parties to a videoconference.
As so-called "videoconferencing" applications are incorporated into personal computers to allow audio-visual interaction of a person with a machine, and possibly through a telecommunications system, interaction between two or more other persons is made possible. In such systems, a user will look at a screen, which may be a cathode ray tube, liquid crystal display, or other type of display which can present an image, while communicating with or through the machine. A system of this type is disclosed in the U.S. Pat. No. 5,374,952 to Daniel P. Flohr, the subject matter of which is incorporated herein by reference.
Existing videoconferencing systems of this type provide an electronic camera to capture an image of the user, which is rescanned periodically. Because the line of sight to the screen should not be obstructed, cameras are placed above or beside the screen. This placement, however, necessitates an orientation of the camera such that the user, while interacting with the machine, is generally looking away from the camera. This is especially obtrusive if the eyes are aimed toward a point laterally displaced from the camera. Thus, in a videoconferencing situation, a face-to-face communication is difficult, because the user must either look at the screen, where an image of the person he is communicating with is located, or at the camera, but not both. In the general arrangement the screen is large enough, and the person sits close enough to the screen, such that the camera and screen are not within the cone of high visual acuity simultaneously.
In order to address this problem, it has been proposed to place the lens and part of the electronics or fiber optics on the end of a goose neck arm, to allow the lens to be positioned near the screen. This goose neck arm, however, is not transparent, and therefore obstructs view, when placed in front of the screen.
An alternative system employs a screen which is small, or placed far from the user. These diminish the perceived quality of the communication. When a large screen is available, i.e., one which is greater than 7" diagonally, it is preferred that this screen, for individual videoconferencing purposes, be located 25-75 cm from the user. Increasing the distance from the user or reducing the size of the screen or the image on the screen, impedes the personal nature of the communication.
A further alternative system employs a so-called "heads-up display", wherein an image is optically projected without a screen in front of the user. This requires a complex headset or projection system, and results in an image of a person wearing the headset or in a special environment.
It is also known to use a full screen size partially reflective filter in front of the screen to allow a frontal image of the user to be reflected to an electronic camera, as shown in the U.S. Pat. No. 5,117,285 to Nelson et al. and the U.S. Pat. No. 5,257,306 to Watanabe. These arrangements necessitate a large optical surface which produces reflections and diminishes the perceived display brightness. The U.S. Pat. No. 5,257,306, incorporated herein in its entirety by reference, provides a system in which the optical orientation of the user with the system may vary, to allow a large videoconference to have a "central" figure with others peering toward him or her on screen.
An image of a user may also be used for non-keyboard communication with the machine, whether in the context of a videoconferencing system or not. For example, an optical gaze position sensor is known which employs an electronic camera. This system may also benefit from a frontal image rather than one which is skewed because the user is looking at the screen rather than the camera.
For video interface applications, a system should include:
(1) an image display, i.e., the screen;
(2) an image input device, e.g., a video camera;
(3) an acoustic annunciator, e.g., a loudspeaker;
(4) an acoustic signal input, e.g., a microphone;
(5) a control for the audio system, preferably including a half duplex audio control or an echo cancellation system for full duplex operation;
(6) a control for the image systems, preferably including video conversion for the transmitted and received signals.
When the screen is a part of a digital computer, the image is displayed through the computer circuit, preferably through a so-called "video window controller" or "video controller". The image on the screen may encompass the entire active display area, or other data may also be simultaneously presented.